"THIS building would be wonderful anywhere, but in Washington it's astounding!"

That was the verdict of one New York magazine editor in town for a preview of "406," the renovated building at 406 7th St. NW, where six art galleries have blossomed forth from the rubble of downtown Washington.

Last week the elevator still wouldn't work, but dealers were flying high as they scurried about getting pictures hung and labels in place for the press preview tomorrow, the patrons' preview Tuesday and the public opening Wednesday.

The arrival of "406" is clearly more than just another opening.With its 20,000 square feet and 18-foot ceilings, "406" easily equals -- and in many ways surpasses -- 420 West Broadway in New York's SoHo as the handsomest, most enviable commercial art space in America. Containing four of the city's best dealerships -- along with two new ones from Baltimore and New York -- it marks a shift in the center of the Washington art scene from the P Street Strip to downtown. And it marks the growing maturity of the nation's second-largest art market.

Just one block from Pennsylvania Avenue, halfway between the National Collection of Fine Arts-National Portrait Gallery complex and the National Gallery, the Hirshhorn and other Mall museums (with Metro stops at either end), "406" is bound to snag a goodly number of the millions who visit those museums each year.

"The building does everything we'd hoped," said architect David Schwarz, grinning as he strolled through the dramatic, angled spaces he has carved from the abandoned structure. "Each gallery is different, just as their art is different -- yet each has a sense of both path and place."

The six dealers seemed equally pleased. "The farthest back you could stand from a painting on P street was 11 1/2 feet," said dealer Diane Brown as she exulted in the 37-foot expanse between herself and the opposite wall, already covered with the brightly colored paintings of Robert Kitchen.

In her former P-Street space, with its small stairways and low ceilings, Brown could not even show the large-scale sculpture she was selling. Ironically, she can't get the giant sculptures up these stairs either, and the elevator isn't working. So she will maintain her downtown "Sculpture Space" on O Street NW.

"It's so civilized," said Nancy McIntosh Drysdale (like Brown, a P-Street refugee), awash in the multi-colored neon of a Dan Flavin sculputure, one of several minimalist works in her opening show. a

"I've seen few spaces anywhere in the world to compare with this, except in Barcelona," boasted Ramon Osuna, who shares the second floor with Drysdale. As the phone jangled endlessly last week, he sat in a Napoleonic chair stroking his beard, surrounded by every dealer's dream come true: an elegant office with ice bucket at the ready, a private viewing room, an easy-access storage area, broad expanses of exhibition space and the atmosphere of elegance and success that is so comforting to buyers when they spend large chunks of cash.

"It's extraordinary space. That's why I'm here," said Angus Whyte, formerly of New York and Boston where he was associated with Robert light, one of the country's most highly-respected dealers in fine old master prints and drawings. c

Whyte -- whose gallery boasts a harpsichord -- will open with a show of giant contemporary abstract paintings by one Franklin Tartaglione, rather than with the old and modern master prints and drawings for which he is best known. But he also has works by Durer, Rembrandt, Fantin-Latour, Redon, Pissarro and Ensor -- along with some early 20th-century Americans, among them Bellows and Sloan -- which can be seen for the asking.No one could remember the last time a good Durer or Rembrandt had been offered for sale in a Washington commercial gallery.

Whyte and Brown share the top floor at "406" with Harry Lunn, whose two-tiered space is the most spectacular of all. Already dubbed "Lunn's Lair," the 18-foot ceilings here slope down to 14 feet to enclose a balcony-loft with a private office, a research library and a full kitchen, already stocked. The lower level houses a private viewing room, an administrative area with frame and mat-making facilities, a gentlemanly shower, and exhibition space, where a survey of Lunn's 19th- and 20th-century photographic holdings will be the opener.

"I believe this will be the start of a new commercial scene that will rival 57th Street in New York," said Bob Lennon, owner of Artransport (an art moving company) who with dealers Osuna, Drysdale and Lunn holds the eight-year lease on the property.

Lennon's optimism is understandable: If his plans materialize, he could end up as the biggest art landlord in the country. In addition to "406" and another building at 501 7th St. NW -- due for renovation soon -- he also holds the 99-year lease on 50,000 square feet of Gallery Row across the street. The $2.7-million renovation of that space is due to begin on Oct. 1 with a $1.2-million grant from the Department of Housing and Urban Development, signed and sealed last week. That building will ultimately house -- Lennon hopes -- three restaurants, a bank, a bar and 10 art galleries.

The "406" project began two years ago, Lennon said, after he read a newspaper story about the arts downtown. He scoured the neighborhood for potential gallery space, and approached the Pennsylvania Avenue Development Corporation (PADC), which has eminent domain over all streets adjacent to Pennsylvania Avenue. "They'd been busy buying and condemning property," Lennon said, "but I was the first to suggest putting something back downtown. They loved the idea." So in partnership with developer Stanley Westreich, he took the lease on six burnt-out buildings on 7th Street, now called Gallery Row, at a cost of $40,000 per year.

In April 1978 Lennon invited most of the top dealers in town to a luncheon at the Palm. "It was the first time they'd all eaten together," he chuckled. a"When they all started looking at what they were paying in rent, and the space they had, and saw the mobs lining up at the East Wing at the National Gallery, and the possibilities opened up by Metro, they almost all decided to take space in Gallery Row."

At the same moment, P Street was in the process of being transformed, with parking lots giving way to new condominiums and a hotel conversion at 2121 P affecting five dealers -- who were put on month-to-month leases at spiralling rents. Just when they all decided to move, they suddenly found that they had nowhere to go. With interest rates approaching 22 percent, the Gallery Row project had been postponed. Lennon scrambled for a solution that would protect his investment, and found the space at "406" available with an eight-year lease. He grabbed it with Lunn, Osuna and McIntosh, who each came up with $100,000 to remodel the space in addition to the $10 per square foot they'll be paying to lease the building from Lennon.

With a museum-quality show of 17th- and 18th-century colonial paintings from Peru glowing from his walls, Ramon Osuna was the first to have his gallery in picture-perfect shape for the opening. Last to be ready will be Baltimore's leading private dealer, Barbara Kornblatt, who leased the ground-floor space only last week, and will not be ready to open until mid-november.

In Baltimore Kornblatt has shown Robert Motherwell, Hans Hofmann, Sol Lewitt and Frank Stella, along with some of the same artists, along with large-scale sculpture, paintings and prints. She has a one-year lease, and will maintain her Baltimore gallery. "I'd throught of coming to Washington earlier, and liked the community of P Street, but architecturally I couldn't survive that space," she said, adding that her decision to move now came as a result of the "combination of space, location and timing. Washington is a bigger market, after all, and I wanted to add to what I was doing in Baltimore."

Meanwhile, several of the dealers who insist they're staying on P Street and in Georgetown have been seen prowling the downtown area for space, according to Osuna.

Chris Middendorf and Louis Andre have taken more decisive steps. They revealed last week that they are negotiating for a lease on three stories over the Golden Palace Restaurant near 7th and G Streets. "If it goes through, we'll open an adjunct gallery called BPI [Big Pictures Inc.] and show large-scale works in conjunction with shows at Middendorf/Lane on Columbia Road," said Middendorf. According to him, Louis Andre, whose Georgetown gallery closed two years ago, will reopen in the space. He added that Barbara Fiedler and Gerd Sander have also expressed interest in the enterprise.

"All the good dealers will have to come down here eventually," said Lennon.

But will they? Will the P-Street transplant take?

"They said '406' could never happen, but it has," reminded Harry Lunn.